The Auschwitz Museum in Poland announced it rediscovered thousands of personal items that belonged to Jews killed in the concentration camp, the same week that three US senators, an Academy Award-winning actress, and the president of the World Jewish Congress said it's a "moral duty" to ensure Holocaust victims' families can recover art stolen from them during World War II.

"Art restitution is about preserving the fundamental human condition," Dame Helen Mirren, who starred in "Woman in Gold," about one woman's fight to recover her family's looted artwork, said to a panel of senators at a Tuesday hearing. "It gives Jewish people – and other victims of the Nazi terror – the opportunity to reclaim their history, their culture, their memories and, most importantly, their families."

The legislation Mirren and a bipartisan group of senators promoted Tuesday, which would loosen the statute of limitations for families to recover looted art, is part of an effort to provide a more tangible restitution to Holocaust victims and their families. Soon after the war, many countries arranged monetary compensation and social services, followed by education campaigns. However, in many cases, efforts to return the physical belongings of Holocaust victims to their rightful owners – including valuable pieces of art – lagged, sometimes for decades.

"What makes this particular crime even more despicable is that this art theft, probably the greatest in history, was continued by governments, museums and many knowing collectors in the decades following the war," Ronald Lauder, president of the World Jewish Congress and the former US ambassador to Austria, said during the Senate hearing. "This was the dirty secret of the post-war art world, and people who should have known better, were part of it."

The thousands of belongings the Auschwitz Museum rediscovered are unique, however, because they were simply forgotten about. The roughly 16,000 items – which include jewelry, kitchenware, cutlery, and watches – were originally uncovered near the camp's gas chambers in 1967, then individually catalogued and placed in 48 cardboard boxes.

Presumably, they were meant to be analyzed and studied, Piotr Cywiński, the director of the museum, said in a statement. However, a political crisis broke out in Poland, likely delaying the research.

After students protested against the Polish People's Republic in 1968, the communist regime clamped down on any political dissent. This was accompanied by an anti-Semitic campaign the regime branded as "anti-Zionist," prompting thousands of Jews to emigrate from the country.

"Perhaps, that is why they did not hurry with the implementation and closure of this project," said Mr. Cywiński. "The times then were difficult for topics related to the Holocaust."

The artifacts, meanwhile, remained in their cardboard boxes in the Polish Academy of Sciences, and were forgotten about.

Cywiński said the discovery will not only offer further testimony about the history of Auschwitz, but also a "moving, personal" testimony to the victims. "In most cases, these are the last personal belongings of the Jews led to death in the gas chambers," he said.

Other family heirlooms and religious objects are suspected to be in a number of other museums in Poland, according to a paper presented at the Conference on Jewish Material Claims Against Germany. It is estimated up to 1 percent of all items in Polish museums were previously owned by Jews.

Mr. Lauder, the president of the World Jewish Congress, hopes the Senate legislation can play a part in righting this wrong.

"I wish this legislation had happened 10 or 20 years ago, but the fact is that it's happened, it's going to have a major effect on the future," said Lauder. "And many works of art – I use the expression 'the final prisoners of World War II' – will finally find their rightful owners."